1. Field of the Invention
This invention generally relates to transport trays used to insert and extract compact disks (xe2x80x9cCDsxe2x80x9d) into and out of CD drives (xe2x80x9cdrive(s)xe2x80x9d). More particularly, this invention relates to the CD transport tray drive mechanisms used to power transport trays into and out of these drives.
2. Statement of the Problem
Reading from, and writing to, a CD involves loading and unloading the CD into and out of a CD drive. These loading and unloading operations are usually carried out by a CD transport tray. For example, copying information stored on a first CD onto a second, blank CD is often accomplished by (1) placing the information-containing first CD on a CD transport tray, (2) loading said tray (and the first CD that rests upon it) into a drive, (3) copying information on the first CD on a hard drive component of the system, (4) unloading the first CD from the disk transport tray, (5) replacing the first CD with the second, blank CD, (6) loading the tray (and the second, blank CD resting on it) back into the drive, (7) copying the information taken from the first CD and stored in the hard drive onto the second CD, and (8) removing the transport tray (and the second CD resting upon it) from the drive. In order to do all of this, the transport tray must be moved laterally from a fully open position, where the compact disk can be placed on the tray (or removed from it), to a fully closed position (such that a CD on the tray is placed in a specific operating position inside the drive) where the CD is xe2x80x9cread fromxe2x80x9d or xe2x80x9cwritten toxe2x80x9d and thereafter moved back to its fully open position (such that the second CD on the tray is again carried outside of the drive so that it can be removed from said tray). A mechanical drive mechanism provides the powered lateral motion needed to move the tray back and forth between its fully open position and its fully closed position.
Most prior art CD transport tray drive mechanisms employ rack and pinion gear systems. The rack is an extended, bar-like, member having gear teeth along a major portion of its length. These teeth engage the teeth of a powered pinion gear. The rack component of such a system is usually on the underside of the tray. The powered, pinion gear is attached to another part of the drive. When engaged with the pinion gear, the rack is driven laterally as the pinion gear rotates. Depending on the direction in which the pinion gear rotates, the CD transport tray is either driven into or out of the drive.
These rack and pinion transport tray drive mechanisms are powered by electrical motors capable of being driven in either a clockwise direction or a counterclockwise direction. Such electrical motors have a drive shaft that is connected to a pulley head. The motor pulley head is connected to mechanical means for transmitting the rotary motion of the motor pulley head to the gear train. For example, the motor pulley head may be connected to an elastic belt or band that is, in turn, connected to a gear train pulley head. Thus, the powered rotation of the motor is transmitted to the gear train pulley head via movement of the belt. This causes the gear train to drive the pinion gear which, in turn, causes the rack to be driven laterally.
Those skilled in this art, also will appreciate that the electrical motors used in such transport tray drives turn at speeds or angular velocities that are greater than the desired speeds of such pinion gears. Thus, the speed of the pinion gear relative to the speed of the motor drive shaft must be reduced. This is generally done by a series of gears in a gear train wherein a first, driving, gear has a diameter that is smaller than a second, driven, gear with which the first gear engages. This xe2x80x9cgearing downxe2x80x9d in transport tray drive mechanisms is usually repeated through use of two or three succeeding gear pairs wherein succeeding driving gears have a smaller diameter than the driven gear. Eventually the last gear in these gear trains is connected to a pinion gear that rotates at a speed that is less than the speed of the motor shaft.
The engagement of the teeth of the pinion gear with the teeth of the rack can, however, create potentially harmful stresses in the individual teeth of the pinion gear and/or of the rack. This mechanical engagement also tends to produce noises having sound levels that are sometimes greater than about 70 decibels. Such sound levels are generally regarded as being esthetically undesirable in the CD drive industry. Heretofore, these potentially harmful stresses (and unaesthetic sounds) have been mitigated by the xe2x80x9cgivexe2x80x9d, xe2x80x9cplayxe2x80x9d, xe2x80x9ccushioning effectxe2x80x9d, etc. that is provided the engaging action of the rack and pinion by a certain degree of xe2x80x9cslippagexe2x80x9d in the pulley system that connects the motor to the gear train. For example, if the engagement of the teeth of the pinion gear with the teeth of the rack is particularly stressful, the pulley belt can momentarily xe2x80x9cslipxe2x80x9d with respect to the turning pulley heads and thereby relieve the stress between the engaging teeth of the rack and pinion gears.
This prior art method of relieving the potentially damaging stresses placed on engaging and disengaging rack and pinion gears does however have certain drawbacks. For example, this method of relieving such stresses requires the use of three mechanical elements (i.e., a motor pulley head, a gear train pulley head and a pulley belt that connects them) that all add to the cost and mechanical complexity of transport tray drive mechanisms. Problems also arise from the fact that the pulley belts that connect the motor to the gear train tend to lose their elasticity and/or break over time.
Applicants have found that the potentially harmful forces (and unaesthetic noises) created by stressful rack and pinion gear engagements and/or disengagements in CD tray drive mechanisms can be greatly reduced through use of friction-based, engaging surfaces that are used in place of gears. Thus, instead of a pinion gear having teeth, applicants"" transport tray drive mechanism employs a drive wheel that is made of an elastomeric material or, in the alternative, employs a drive wheel having a rim that is made of, or covered by, an elastomeric material such as a natural or synthetic rubber. That is to say that the rim of the wheel may be made of an elastomeric material by virtue of the fact the drive wheel itself is made of an elastomeric material, or the drive wheel may be provided with a xe2x80x9ctire-likexe2x80x9d rim which is made of an elastomeric material. This wheel or a rubber rim thereof is placed in friction-creating contact with a strip or bar on the transport tray. In other words, this strip or bar does not have teeth such as those employed in the rack component of prior art transport tray drive mechanisms. Such a strip or bar is elongated (i.e., it runs over a major part of the length of the tray) and is preferably made in an injection molding operation that creates a monolithic tray/strip or bar component. The strip or bar also may be provided with a strip of elastomeric material. These engaging surfaces (be they elastomeric materials or polymeric materials) may have textured, or smooth outermost surfaces. An elastomeric strip placed on the polymeric strip or bar may be the same elastomeric material from which the drive wheel or the drive wheel rim is madexe2x80x94or the elastomeric strip can be made of a different elastomeric material. The resulting elastomeric material-to-elastomeric material engagement may give better traction then an elastomeric material wheel or rim/molded polymeric material system.
Use of this arrangement, implies that any potentially stressful forces produced by engagement of such a drive wheel and such a strip or bar on the tray are compensated for xe2x80x9con the spotxe2x80x9d by the xe2x80x9cgivexe2x80x9d, xe2x80x9ccushioning effectxe2x80x9d, xe2x80x9cslippagexe2x80x9d, etc. provided by the natural elasticity of the elastomeric material on the rim of the drive wheel (and, optionally, by any elastomeric material on the strip or bar on the transport tray). Thus, any potentially damaging forces created by the friction engagement of the rim of the drive wheel and the strip on the tray are not transmitted through the gear train as they are in the prior art case previously described where the give, cushioning effect, etc. is provided by slippage of a pulley beltxe2x80x94after the potentially damaging forces are transmitted through the gear train. The cushioning effect provided by the elastomeric rim of the drive also serves to lower those noises associated with the operation of the CD. Applicants also have found that the manufacturing tolerances for the moving parts of the drive mechanisms of this patent disclosure can be increased while fewer parts than a belt system are required. This implies that the cost of the hereindescribed CD transport trays will be less than gear driven mechanisms.
Thus, at its most fundamental level, applicants"" invention employs a powered drive wheel having a radial drive surface, rim, etc. that is made of an elastomeric material (rather than gear teeth such as those on pinion gears) and which, by means of a friction-based driving action, engages a flat strip, bar, etc. on the transport tray in order to power said tray into or out of the CD drive. This flat strip, bar, etc. on the tray may be provided with a strip of elastomeric material (rather than gear teeth such as those on prior racks) that serves to create friction-based forces between the drive wheel and the strip or bar on the tray. It might also be noted here that, for the purposes of this patent disclosure, the expressions xe2x80x9csmooth, radial drive surface, rim, etc.xe2x80x9d should be taken to imply that the drive wheel has no gear teeth on its radial, strip-engaging, surface, rim, etc. Other parts of the drive wheel, however, may well be provided with gear teeth (e.g., such as those that engage with a gear in the gear train that is connected to the motor). Similarly, the expressions xe2x80x9cflat strip, bar, etc.xe2x80x9d on the tray should be taken to imply that the strip, bar, etc. has no gear teeth on its rim-engaging surface.
The elastomers used to create applicants"" friction-based, tray driving actions can be made from a wide variety of natural or synthetic elastomeric materials. Such materials are usually polymers possessing elastic (rubbery) properties. These polymers are typically comprised of molecules that are, for the most part, multiples of certain low-molecular-weight monomer units. By way of example only, the rim and/or strip elastomeric surfaces used in this invention could be made of isoprene (2-methylbutadiene-1,3) which is made up of C5H8 molecules. Polyisoprene, which is made of (C5H8)x monomer units (wherein x normally runs from about 1,000 to about 10,000) also could be used for this purpose. Those skilled in this art will appreciate that, although they differ in composition from natural rubbers, many such high-molecular-weight polymeric materials are termed xe2x80x9csynthetic rubbersxe2x80x9d. In any case, other synthetic elastomeric materials that could be used in the practice of this invention would include, but not be limited to, styrene-butadiene rubbers, butyl rubber, acrylonitrile-butadiene rubbers, polyurethanes, polyacrylate elastomers, silicone elastomers and ethylene-propylene elastomers.